(1) Field of the Invention
This invention relates, in general, to a loud speaker system and, more particularly, to a direct/reflecting speaker system incorporating a triangular-shaped enclosure enabling its exact placement in the corners of a listening room.
(2) Description of the Prior Art
In sound reproduction systems utilizing loud speakers it is, of course, desirable that the sound be produced with the utmost possible realistic effect. However, just as the size and shape of a performing hall affect the sounds created, several characteristics of the room where music is reproduced also affect the way that it sounds. The size of the room, its construction, and its furnishing can cause spectral imbalances by absorbing or exaggerating different frequencies in the music.
Given these variables, and because the last component in any audio system is a listening room, it is really impossible to design a speaker to work perfectly in every room. As a result, speaker designers have attempted to compensate with controls which affect the frequency response of the speakers by boosting or cutting the output of different drivers; however, the range of this type of control is severely limited by the frequency ranges of the different drivers.
Conventional speaker designs also attempt to compensate with various types of bass and treble controls. But these controls, designed according to standardized, easy-to-manufacture formulas, are simply inappropriate to cover the groups of frequencies in proportion necessary to control the many variables in room acoustics.
More recently speaker design has investigated the various critical aspects of room acoustics, and the lack of standardization in the recording industry as to variations in frequency response. As a result some speakers now are provided with controls to compensate for frequently occurring problems caused by room acoustics and recording techniques.
At a live performance, music which reaches one's ears comes not only directly from each instrument, but from every surface in the concert hall or the like which reflects the sound. The high proportion of reflected sound, as a matter of fact, is what gives a live performance its richness, depth, and spaciousness.
For a music system to more clearly recreate a live performance, it must be able to reproduce in one's listening room, the spatial image, i.e., the combination of direct and reflected sound, associated with a live performance. Nevertheless, up until only a few years ago, loud speaker systems conventionally radiated sounds almost totally direct. And full stereo sound could only be heard directly in front of, and between, a pair of speakers.
In U.S. Pat. No. 2,896,736, which issued July 28, 1959, to J. E. Karlson, there is disclosed an acoustic system involving a reflection type loud speaker. As disclosed in that patent, a sound reproducing loud speaker is located in an enclosure in such a manner that sound emanating therefrom is directed against a suitable wide sound reflecting surface. This surface, according to the patentee, can be either a flat or curved wall. Thus, a sound image is established which gives the impression to listeners of having emanated from substantially an entire reflecting wall, rather than the loud speaker itself. The sound, moreover, appears to have originated from some point beyond the reflecting wall and thus creates the effect of additional acoustic spaciousness. According to the patentee, however, the speaker enclosure must be spaced sufficiently from the wall that the reflected sound path completely avoids the loud speaker and its enclosure.
Although corner placement of the loud speaker in U.S. Pat. No. 2,896,736 is disclosed, and results in very interesting dual sound effects because each of the walls appear to be an individual sound, only a minor image effect, according to the patentee, is created. The composite effect is considerably different than when a single wall is used as the principal reflecting plane. Moreover, as disclosed in the patent, the corner placement of such a speaker system as disclosed produces less realistic and natural acoustic effects and should not be regarded as wholly equivalent to the use of a single reflecting wall.
While others than Karlson (U.S. Pat. No. 2,896,736) have heretofore disclosed speaker systems for corner placement in a listening room, none of them of which I am aware, including Karlson, have disclosed a direct/reflecting speaker system, and exact corner placement, such as set forth herein. Moreover, none of the corner placement speaker systems invented before my invention, and of which I am aware, will provide the spaciousness of sound, as will my speaker system, while at the same time offering a speaker system that is not only economical but simple and compact in construction.
According to the disclosure in U.S. Pat. No. 3,923,124, the performance of most speakers is enhanced when the speaker is specifically designed for placement in the corner of a room. In such a design, according to the patentee, the speaker is usually triangular in shape, with the front panel facing outwardly into the room and side panels converging inwardly from the sides of the front panel to the back edge, or corner of the enclosure, facing the corner of the room. Two features of speaker response, according to the patentee, generally enhanced by corner placement of the speaker, are an improvement in bass response and an improvement in sound direction and dispersion in the listening room. Even so, the patentee fails to disclose whether such a corner placed speaker involves only direct sound, reflected sound, or a combination direct/reflected sound.
The speaker system actually disclosed in U.S. Pat. No. 3,923,124, while involving corner placement, is a backloaded folded horn comprising direct radiating low, mid-range, and high frequency drivers. The low frequency speaker is backloaded by the horn whose outlet faces into the corner of the room. The horn continues to expand from the horn outlet through a space between the side panels of the speaker enclosure and the walls forming the corner of the listening room, to the mouth of the horn at the front of the speaker enclosure.
In STEREO, Volume 10, No. 2, 1977, there is disclosed THE ALLISON: THREE System which, according to the author, is meant for corner placement, and moreover, whose efficiency and sound is augmented by the corner placement. This speaker system, as disclosed, comprises a 10-inch woofer, a 31/2-inch mid-range driver, and a 1-inch tweeter, all of which are located on the front face of the enclosure, which is of triangular-shaped cross-section, in, more or less, superposed fashion. Thus, the woofer is placed at the very bottom, roughly equidistant from the floor and walls, the mid-range driver is located about 311/2-inches off the floor, and the tweeter just above that at 371/8-inch height.
One of the problems with regard to corner placement of speakers, as set forth by the author in STEREO, is that with such a placement of the speakers one finds an absent or unstable center image-the so-called "hole-in-the-middle". However, quite advantageously and surprisingly, the author claims THE ALLISON: THREE Speaker System results in a very good center, indicating exceptionally good dispersion throughout the audible range.
The stereo image of THE ALLISON: THREE Speaker System moreover, is such that the sound appears to come from a broad region between the two speakers placed in the adjacent corners on the same wall in the listening room. Thus, the sound does not appear to come from the loud speakers at all. As a result, there is no "optimum listening area"; the listener location is not at all critical, as is the case in some stereo systems.
U.S. Pat. No. 3,983,333, which issued to Allison Acoustics, Inc. on Sept. 28, 1976, is believed to disclose, in FIG. 15 thereof, THE ALLISON: THREE Speaker System. As disclosed therein, in FIG. 15, the triangular-shaped speaker enclosure is located directly in the corner of the listening room, the sides of the speaker enclosure flush against the corner walls. Direct radiation audio reproducer means are mounted flush in the front panel of the speaker enclosure, the bass driver being located at the bottom, near the floor, and the middle and high frequency speakers located one above the other nearer the top of the enclosure.
The loud speaker system disclosed in U.S. Pat. No. 3,582,553 provides both direct and reflected sound to the listener so as to, according to the patentee, more nearly simulate the character of the sound heard in a concert hall. As disclosed in that patent, there is provided a loud speaker system which comprises an enclosure which comprises at least two normally rear baffles forming an angle with each other, and a front baffle which is situated normally parallel to a wall in a listening room. The rear baffles preferably contain a number of closely spaced, full-range, high compliance loud speakers which are connected in phase and nearly fill each rear baffle, and the front panel, preferably comprises a baffle containing at least one small loud speaker cophasally excited with certain of the other small loud speakers, for providing direct sound to the listener. Nevertheless, according to the patentee, an especially compact and inexpensive embodiment of the invention might include just one loud speaker on each rear baffle and one on the front baffle, with the front loud speaker energized through an attenuating network that delivers about 11/4 the high frequency energy to the front speaker than is delivered to each of the rear loud speakers. A feature of the invention resides in minimizing undesired resonances. Thus, there are a number of baffles each containing at least one loud speaker, but none of these baffles are parallel to another surface.
Although conceivably the loud speaker enclosure disclosed in U.S. Pat. No. 3,582,553 can be of triangular shape, there is no suggestion by the patentee that such a speaker system could actually be used in a corner placement. As a matter of fact, the speakers are only disclosed as being in spaced-location, about a foot from a wall of the listening room, and with the front baffle parallel to the wall, the loud speaker enclosure being located on the center line of the room. Where two speaker systems are used, the loud speaker enclosures are provided in spaced-apart location along one wall of the room, the front baffles of each speaker being in the same plane parallel to the said wall. Thus, corner placement would not be conceivably possible to accomplish the results intended by that patentee.
One of the principal problems encountered in designing a speaker system and enclosure for home use is optimizing design characteristics so as to reach a suitable compromise between two continuously conflicting design perimeters, one being the acoustic performance of the speaker and the other being aesthetic and financial considerations that place practical limitations on the size and the expense of any speaker system.